Hyperthermia (i.e., thermal therapy or intentionally induced above normal temperature, has proved to be beneficial in treating tumors (both benign and malignant growths) in animals and humans. External wave guide applicators have been used to treat superficial lesions; wave guide applicators positioned around a body or limb have been used in an attempt to heat deep seated lesions; interstitial (within the tissue) antennas have been employed to invasively treat tumors such as unresectable breast cancer; and intracavitary (inside a naturally occurring cavity, a.k.a. intraluminal, endotract, etc.) approaches have been employed to heat growths in, and adjacent to, naturally occurring cavities such as the esophagus and the prostatic urethra.
Attempts to employ EMR to heat subsurface growths ordinarily result in temperatures in the intervening normal or non-targeted tissue reaching hazardous levels before the tumor or target tissue temperatures reach prescribed thermal dose levels. The advantage of interstitial and intracavitary approaches is that the applicator is positioned inside or adjacent to the target tissue. Thus, heating is localized to the area immediately around the source of the EMR, is confined to the target tissue, and does not overheat significant amounts of non-targeted tissue before reaching the desired temperature in the target tissue.
The major advantage of an intracavitary approaches is that it is minimally invasive (unlike interstitial techniques), non-surgical, and allows direct access to the target tissue.
The terms hyperthermia and thermal therapy are used herein interchangeably. Hyperthermia is broadly defined herein as any above normal temperature and includes terms of fever (37-41.5 degree C), hyperthermia (typically defined as 41.5-45 degree C), thermal therapy (typically defined as 45-55 degree C), coagulation necrosis (&gt;55 degree C), cauterization, etc.
U.S. Pat. No. 2,407,690 by Southworth teaches the advantages of using external wave guide apparatus for diathermy and how the wave can be directed down tubular orifices. But the Southworth body passage insertable waveguide applicator concentrates the heating pattern at the radiating tip of the applicator. Thus, the use of Southworth type applicator results in non-uniform heating of the tissues along the length of a tubular organ.
U.S. Pat. No. 4,154,246 by LeVeen describes an RF helical antenna with the helical antenna coils wound tightly together (i.e., windings without any space therebetween) for interstitial and intracavitary use. The LeVeen helical coil antenna propagates energy from the distal tip of the applicator.
U.S. Pat. No. 4,658,836 by Turner is stated to be for a microwave antenna that provides uniform heating along the length of the esophagus.
U.S. Pat. No. 4,700,716 by Kasevich et al discloses a device that provides uniform heating along the entire length of the applicator array.
Dipole type antennas have been employed in intracavitary applicators, but such type of applicators concentrate the energy propagation and result in a heating pattern around the "junction" that is proximal to the distal tip of the antenna.
U.S. Pat. No. 4,825,880 by Stauffer et al., illustrates an implantable helical coil antenna adaptable for interstitial hyperthermia that is designed with a "gap" between the proximal end of the coil and the outer coaxial conductor. This design provides uniform heat along the active length of the coil and the heating pattern is unaffected by the insertion depth.
U.S. Pat. No. 4,583,566 by Hines describes a helical antenna that is substantially equivalent to the Stauffer et al., design except that there is no "gap", in that the proximal end of the antenna coil is connected to the outer conductor. In the Haines patent, it is contended that the design provides more uniform heating along the length of the coil.
U.S. Pat. Nos. 5,097,845 and 4,841,988 by Fetter et al., describe a helical coil antenna that is similar to the Hines design, except that the separation between the windings varies in an attempt to provide uniform heating along the axial length of the antenna.
Intracavitary hyperthermia has been employed to treat cancer of the prostate (CaP), benign prostatic hypertrophy (BPH), and other conditions of the prostate. Both atransrectal and transurethral treatment approaches have been developed.
Mendecki et al., described in a publication entitled "Microwave Applicators for Localized Hyperthermia Treatment of Cancer of the Prostate"; Int. J. Radiation Oncology, Bio., Phys., Vol. 6, pp 1583-1588), 1978, a transrectal applicator with a dipole antenna for the treatment of CaP.
U.S. Pat. No. 4,311,154 by Sterzer et al., describes a transrectal applicator (identical to that described by Mendecki, et al) that is equipped with a temperature sensor in a transurethral catheter to monitor temperatures.
Yerushalmi et al., published an article "Normal Tissue Response to Localized Deep Microwave Hyperthermia in the Rabbit's Prostate: A Preclinical Study"; Int. J. Radiation Oncology, Bio., Phys., Vol. 9, pp 77-82, 1982, describing the results of transrectal hyperthermia experiments on rabbit tissue. U.S. Pat. No. 4,601,296 by Yerushalmi describes a transrectal applicator with channels for circulating a cooling agent around the surface of the applicator to spear the rectal wall tissues in contact with the applicator. Subsequently, a number of publications and patents have been issued for different designs for transrectal applicators (e.g., Eshel, European patent application 0 248 758 A1; and Eshel et al., U.S. Pat. No. 4,813,429).
Transurethral hyperthermia has been employed to principally treat benign prostatic hyperplasia (BPH). Mebust reports in the editorial comments section of another publication entitled "Transurethral Hyperthermia for Benign Prostatic Hyperplasia; Preliminary Clinical Results"; The Journal of Urology; Vol. 143, May, 1977, that in 1977 a high frequency electrical surgical current was used in a transurethral approach to treat patients with BPH.
As described in the article entitled, "Microwave Surgical Treatment of Diseases of Prostate"; Urology, Vol. XXVL, Number 6; pp 572-576, 1985, Harada et al., employed transurethral hyperthermia to treat human patients for CaP and BPH using a rigid microwave monopole antenna to cause coagulation necrosis.
Saprozink publicly disclosed (Mar. 31, 988) in Medical Tribune, "Transurethral Hyperthermia for BPH: Trial's Goal is to Top 80% Success", by Rick McGuire, Thurs., Mar. 31, 1988, pp. 3, 13, 14, a foley catheter built by Astrahan with three EMR antennas, a temperature sensor and a balloon for transurethral hyperthermia for the treatment of BPH.
Turner et al., received U.S. Pat. No. 4,967,765 for a urethral inserted applicator for prostate hyperthermia that contains a single helical coil antenna, temperature sensor means and a balloon.
Hascoat/TechnoMed's European patent application 0 370 890 A1 describes a transurethral catheter with a MW antenna that is positioned with a transrectal ultrasound transducer imaging probe.
Sogawa et al., describes an endotract applicator (U.S. Pat. No. 4,662,383) that employs a balloon to fix a dipole antenna in a tubular organ. The transrectal applicator is shaped to be held in place by the rectal sphincter.
Matsuda's intraluminal applicator described in "Heat Application for Clinical Carcinoma of the Esophagus; Intraluminal hyperthermia for esophageal tumors"; Hyperthermia Oncology 1988, Vol. 2, Special Plenary Lectures, Proceeding from the 5th International Symposium on Hyperthermic Oncology, Kyoto, Japan, Aug. 29 Sep. 3, 1988, pp 715-716, employed a balloon with circulated fluid to position the applicator in the esophagus.
U.S. Pat. No. 4,967,765 by Turner et al., discloses the use of a standard foley balloon catheter in the bladder neck to position the transurethral applicator.
Eshel (European Pat. Application 0 248 758) used a balloon on the posterior surface of a transrectal -applicator to push the anterior surface of the applicator against the rectal wall and posterior lobe of the prostate.
Hascoat (European patent application 0 370 890 A1) employed saline filled balloons as a "radio reflective screen" to protect non-target tissues from microwave exposure.
U.S. Pat. No. 5,007,437 by Sterzer used two balloons; one to position the applicator in the bladder neck and a second to compress the tissues during treatment.
None of the above identified patents or publications suggests the use of intracavitary EMR (microwave) hyperthermia (thermal therapy) as a non-surgical approach to endometrial ablation.